H. E. Richter: Zur Analytik der Pyridoxine 361

reagiert, wurde Ammoniak durch die angefiihrten Basen ersetzt und somit nur noch Pyridoxamin mit den notierten Farbungen zur Reaktion gebracht: Natriumhydrogen- carbonatlSsung griin; verd. Natronlauge gelbgriin; Borax- 15sung rot; Pyridin rotviolett.

Pyridin zeigte neben einem absolut negativen Blindwert die deutlichste Farbreaktion und diente als Base ffir folgende Umsetzungen:

a) Aus/~ehrung in der Mikroelorouvette. Man versetzt 1 Tr. w~13riger PyridoxaminlSsung mit 1 Tr. 1,2-Naphthoehinon- 4-sulfons~ure in Wasser (1,2~ und 1 Tr. Pyridin. Die naeh einigen Minuten auftretende rotviolette Farbe l~il3t sich weder mit Dichlorathan noch mit Amylalkohol aus- schiitteln. Grenzkonzentration 1:50000.

b) Aus]i2hrung in /rischem P]lanzenpreflsa]t. Prel3saft frischer Pflanzen warde auf Filterpapier iibertragen und mit 1 Tr. 1,2-Naphthochinon-4-sulfons~iure versetzt. Eine sicht- bare F~rbung trat nach 4 h auf, die volle AusfKrbung wurde nach 6 h erreicht. Untersucht wurde der Prel~saft aus Bli~ttern yon: Calendula officinalis L. Ringelblume (Com- positae), Chrysanthemum vulgare(L) Bernh., Rainfarn (ComposRae), Inula Helenium L., Alant (Compositae),

Carum carvi L., Kiimmel (Umbelliferae), Ricinus com- munis L. (Euphorbiaceae), Armeniaca vulgaris Lam., Marille (Rosaceae), Persica vulgaris Mill., Pfirsich (Rosa- ceae), Cerasus Mahaleb (L) Mill., Steinweichsel (Rosacee).

L i te ra tur

1. Anger, V. : Mikrochim. Acta 1968, 350. 2. Ben-Dor, L. : Chemist-Analyst 58, 8--9 (1964); vgl. diese

Z. 210, 154 (1965). 3. Feigl, F., Ben-Dor, L.: Talanta 10, 1111 (1963); vgl.

diese Z. 210, 156 (1965). 4. Hakanson, R.: J. Chromatog. 18, 263--265 (1964); vgl.

diese Z. 207, 452 (1965). 5. Maiwald, L., Maske, H. : Z. Physiol. Chemic 806, 143--144

(1956); vgl. diese Z. 159, 450 (1957/58). 6. Wada, H., Snell, E. E.: J. Biol. Chem. 286, 2089--2095

(1961); vgl. Anat. Abstr. 1962, 1239. 7. Richter, H. E. : Mikrochim. Aeta 1962, 455.

Dr. H. E. Richter Botanisches Institut, Tierarztliehe ttochschule A-1030 Wien, Linke Bahngasse 11, 0sterreich

Kurze Mitteilungen

Determination of Copper as Copper Anthranilate and its Separation from Zn ~+, Ni 2+ and Mn 2+ by Precipitation from Homogeneous Solution

Bestimmung yon Kupfer als Kupferanthranilat und dessen Trennung yon Zn 2+, Ni z§ und Mn 2§ durch F~llung aus homogener LSsung

I-IAR]3IR StaGE, D. S. IVh~TAr,, and N. K. M~THVR

Department of Chemistry, University of Jodhpur, Jodhpur (India)

Received September 25, 1970

Copper an th ran i l a t e is r epo r t ed to be p rec ip i t a t ed a t a r a the r low p H (2.78) compared to o ther me ta l ions (Zn2+: p H 4.72; Mn2+: p H 5.15; Ni~+: p H 4.51), b u t due to coprec ip i ta t ion an effective sepa ra t ion is no t possible [1,2] and the reagen t has been descr ibed as non-specific. Hence an inves t iga t ion was u n d e r t a k e n to f ind whe ther the sepa ra t ion of copper an th ranf la te can be done b y i ts p r ec ip i t a t i on f rom homogeneous solut ion (PFHS) . I t has been possible to sepa ra te Cu ~'+ f rom Zn 2+, Mn ~+ a n d Ni 2+ b y P F H S m e t h o d and the p rec ip i t a t e fo rmed b y this technique is non-adher ing, g ranu la r and far super ior for gravi- met r ic analysis . Other m e t a l an thranf la tes , preeipi-

t a r e d a t higher p i t range, also have large par t i c le size compared to convent iona l method .

Experimental

Reagent. Ethyl anthranilate hydrochloride can be synthesised directly by esterification of anthranilic acid with ethanol in presence of hydrochloric acid gas. Suitable solutions (2o/0 wt/vol) may also be prepared from commercially available methyl or ethyl anthranilates by dissolving in dil. hydro- chloric acid.

Procedure. In a 250 ml beaker, a suitable amount of the metal ion containing solution was taken and its pH was adjusted to the desired value (see above) with sodium acetate and/or acetic acid solutions. An excess of the reagent solution was then added and the pl~ of the solution was again checked. The solution was allowed to stand for 40 rain at 80~ when the precipitation was complete. After cooling to room temperature, the precipitates were filtered through filter crucibles and washed. (i) In case of copper anthranilate, the green precipitate was washed with a solution prepared by adding 1--2 ml of precipitating reagent to 1O0 ml of hot water, followed by alcohol, (ii) in case of zinc anthranilate, the white precipitate was washed with a solution prepared by diluting the reagent solution with 15--20 times as much water, followed by alcohol and (iii) in case of manganese and nickel anthranilate, the crystalline precipitate was washed with 96o/o alcohol. The precipitates of the composition M(CTH~O2N)2 were dried at 105-- 115 ~ C.

Resu l t s of de t e rmina t ions were in good agreement wi th those ob ta ined b y convent iona l methods . Copper could be well s epa ra t ed f rom Zn, Ni and Mn.

362 Z. Anal. Chem., Band 254, Heft 5 (1971)

References

1. GSte, H.: J. Chem. Soc. Japan 55, 1156--1163 (1934); cf. Chem. Abstr. 29, 1929 (1935).

2. - - Sci. Rep. Tohoku Imp. Univ., l~irst Serv. 26, 677--687 (1936); cf. Chem. Abstr. 82, 7368 (1938).

Dr. H. Singh Dept. of Chemistry University of Jodhpur Jodhpur (India)

Polarographic Determination of Cd, Co, Mn, Zn, Te(IV) and Cr(VI) in Sodium Azide Solution

Polarographische Bestimmung yon Cd, Co, Mn, Zn, Te(IV) und Cr(VI) in Natriumazidl5sung

A. L. J. RAo and B K. I)URI

Department of Chemistry, Punjabi University, Patiala (India)

Received March 31, 1970; revised January 4, 1971

Sod ium azide has been used in the conduc tome t r i c d e t e r m i n a t i o n of p a l l a d i u m [4]. I n t he p resen t communica t ion this c o m p o u n d has been used as a suppor t ing e lec t ro ly te for s t udy ing the po la rograph ic charac ter i s t ics of Cd, Co, Mn, Zn, Te and Cr a t D.M.E. There are on ly few suppor t ing e lec t ro ly tes in which well defined waves of these e lements were ob t a ined [3]. l~oreover in case of t e l lu r ium and ch romium large m a x i m a a p p e a r in mos t of t he suppor t ing e lec t ro ly tes which are no t suppressed even wi th t he a d d i t i o n of m a x i m a suppressors [1,2].

Ex/gerimental

Equiffment and Solutions. Polarograms were recorded with a manual Adept polarograph at 25 • 0.1~ and the dissolved oxygen was removed by streaming nitrogen. The reference electrode was S.C.E. connected to the cell through agar bridge, saturated with potassium chloride. Double distilled mercury was used and the values of m and t were 2.8 rag/see and 3.0 see, respectively, in distilled water with open circuit. All the metal solutions were controlled by known methods [5]. The pH of the solutions were adjusted with dilute solution of sodium hydroxide and 10~ formic acid.

pH-E]/ect. The proper ranges of pH under which well defined waves were obtained are, Cd 5.5--8.0; Co and Mn 6.5--8.0; Zn 6.0--7.5 and Te 8.5--11.5. In case of Cr at pH 7 to 9.5 two well defined waves were obtained with EI/2 = -- 0.4 V and -- 0.91 V with wave heights in the ratio of 1 : 2. When the pH was raised above 9.5, the first wave merged with the second. At pH 11.0 one wave was obtained with E~/~ -~ -- 0.9 V and the wave height was equal to the sum of the two at pH 7--9.5.

E//ect o] Sodium Azide Concentration. Concentrations of sodium azide from 0.1 M--3 M have no effect on the nature of the polarogram in case of Co, Cd, Zn and Mn but El~ 2 shifted towards the negative potential. In case of Te(IV) and Cr(VI) below 0.3 1~, ia was not constant but attained con- stancy above 0.5 M. ia in case of Te(IV) decreases considerably above 2 M of sodium azide. In case of Cr(VI) the first wave shifted to more negative potential while in the second wave the effect was reverse.

Discussion

The p lo t of log i / ia- - i versus E gave s t r a igh t lines in all the cases a n d the va lue of slopes in case of Zn, Cd and Mn ind i ca t ed t h a t these meta l s undergo rever- sible r educ t ion wi th two-e lec t ron change a n d the va lue of t he slopes in case of Co, Cr a n d Te corre- sponded to an i r revers ible reduct ion .

F r o m the compar i son of the wave he igh t of Co and Te in sod ium azide and a m m o n i a - a m m o n i u m chloride (a l ready conf i rmed [2]) i nd i ca t ed t h a t Co a n d Te undergo i r revers ib le r educ t ion which invo lved two a n d four electrons, respect ively . The wave he ights of the po la rograms of Cr in sod ium azide and po ta s s ium chloride (a l ready conf i rmed [1]) also i nd i ca t ed t h a t t he first wave cor responded to one e lec t ron and the second to two electron.

Since a shif t in El~ ~ t ow a rds nega t ive po t en t i a l u sua l ly ind ica tes the fo rma t ion of s tab le complexes in a g iven media , the na tu r e of the complex m a y be deduced f rom the equa t ion :

d E -- 0.0591 d log (Na Na) - - n /9

Where n a n d I0 have the i r usua l meaning , wi th n = 2, 79 = 2 for Zn, Cd a n d Mn which ind ica te the fo rma t ion of s imple azide complexes.

Relation between Dil /usion Current and Metal Concentration. Pola rograms in 0.1 M sodium azide (0.5 ~[ in case of Te and Cr) for different concentra- t ions of each m e t a l were d r a w n and the diffusion cur ren ts were measu red b y the e x t r a po l a t i on method . The s t ra ight - l ine g raphs ob ta ined ind i ca t ed t h a t t he waves of these m e t a l ions in sodium azide m a y be used for the i r qua n t i t a t i ve de t e rmina t i on in micro- quant i t ies . The po la rograph ic charac ter i s t ics are g iven in the Table .

The de t e rmina t i on of the meta l s is possible in the range of 0 .600--2 .400 ml~I (Cd), 0 .295--2 .062 m ~ (Co), 0 .411--1 .648 m_~ (Mn), 0 .327--2 .616 m ~ (Zn), 0 . 3 2 0 - - 1 . 1 0 6 m l-V[ (Te) a n d 0 .195--0 .780 mM (Cr) wi th re la t ive errors no t exceeding ~ 1 ~

Inter]erences. Elemen t s l ike As, Sb, Bi, Me, In , Fe , Se, V, Zr, Pd , U a n d Ti do no t undergo reduct ion , Th, Pb , TI, Ag, H g and Cu give p rec ip i t a t es as well